Non-photosynthetic functions of carotenoids

Abstract

In addition to their important rôle as accessory pigments in photosynthesis, carotenoids also participate as agents which protect cells and tissues against the potentially harmful effects of visible radiation. They seem to play a unique rôle in this regard, for there are at least three separate mechanisms which can be invoked to explain the protective aspects of carotenoid function. These involve interrupting the potentially destructive photochemical reactions by quenching the triplet state of chlorophyll, physically inactivating the highly reactive singlet state of oxygen ( 1 Δ g ) which can be formed photochemically, and finally serving as an oxidizable substrate to protect other molecules and processes from photodestruction. These protective effects, which were first elucidated in mutant strains of photosynthetic organisms, have been shown to have an even wider role in nature, for many non-photosynthetic systems utilize carotenoid pigments for similar protective purposes.